This invention relates in general to the separation and handling of waste. Embodiments of this invention relate to the solid separation and cleaning of part-liquid animal waste streams.
Concentrated Animal Feedlot Operations (“CAFOs”) are often required to prepare Nutrient Management Plans (“NMPs”) dealing with how the animal waste may be applied to cropland. A number of NMPs are based on the most limiting nutrient found in the animal waste. Federal regulations dictate NMPs, expanding the coverage of the Clean Water Act from the production facility to the land where animal waste is to be applied. Other regulations may dictate how CAFOs prepare NMPs.
In general, the application of waste on the land may be restricted based on the nutrient content and concentration in the waste. Such restrictions increase the competition for and the value of “spreadable” land (land capable of using animal waste as a plant fertilizer), inflating overall manure management costs. In some phosphorus-based NMPs, the overall management costs are even higher since animal waste can contain more phosphorus than nitrogen relative to plant needs, meaning that less waste may be spread on a given acre under such a NMP.
Typical 180 bushel acre corn may require approximately 240 pounds per acre of nitrogen, 100 pounds per acre P2O5, and 240 pounds per acre of K2O, or in other words, a 10:4:10 ratio of N:P:K. Typical swine waste may have an N:P:K: ratio of 10:9:8. Non-efficient recycling of swine waste in such a setting may require recycling only small amounts of swine waste per acre so as to minimize overloading of the land (i.e. accumulation of excess levels of P2O5 not utilized by the crops).
A pregnant sow may produce about 9 pounds of waste per day, with a solid content approximately ranging from 2 to 4.5% solids by volume. Beef cattle with an 800 pound average weight may produce about 48 pounds of waste per day with approximately 15% solids by volume. Dairy cattle weighing an average of 1300 pounds may produce about 50-95 pounds of waste per day with approximately 15% solids by volume.
By separating animal waste into a solid component and a liquid component, CAFOs may be able to handle the animal waste more efficiently. Separated solid components are rich in contaminants, compared to untreated slurry, and may be allowed to collect for longer periods of time before removal. Meanwhile, the liquid component, with reduced levels of contaminants, may be further used, such as for irrigation purposes. Additionally, reduction in the solids component of an animal waste stream may lead to longer life and less maintenance for equipment carrying the waste. Additionally, reduction in the solids component of an animal waste stream may greatly extend the life of settling lagoons.
Current methods of separating animal waste into solid and liquid components are slow processes that often require a very large footprint. Additionally, current methods of separating animal waste into solid and liquid components hinder growth of many operations due to the amount of space and money required to properly handle the increase in animal waste. As well, current methods of separating animal waste into solid and liquid components may not effectively reduce levels of contaminants in the liquid component.
Additionally, animal waste to be processed from certain CAFOs, such as dairy farms, contain a quantity of sand that can have an adverse effect on the life and efficiency of current waste treatment machinery.